In the United States, there are approximately 14 million units of red cell concentrates transfused annually. To address the health risks of bloodborne pathogens, pathogen reduction technologies are being developed for cellular blood products. To inactivate microbes in blood, a microbiocidal compound designated as INACTINE PEN110 is added to the blood and incubated for sufficient time to allow pathogen inactivation to take place. The end result is a biological composition that is relatively free of infectious agents, but that is contaminated with a microbiocidal compound. Removal of INACTINE PEN110 from a red blood cell concentrate (RBCC) currently involves washing the treated RBCC extensively using automated cell washing procedures. While this methodology does remove the microbiocidal compounds, the procedure for cell washing consumes significant quantities of reagents and time. Therefore, there is a need for a more efficient method for removing positively charged microbiocidal compounds from treated biological compositions. The goal of this grant application is to develop a blood filter for removal of the microbiocidal compound PEN110 from blood compositions. The development of the filter will allow the removal of the pathogen inactivating chemical to be accomplished in a more efficient and cost-effective manner. Beyond savings of time and money, the development of the filter will enable the production of safe blood for transfusion in remote areas where cell washing can be impractical including developing nations and military applications. The Phase 1 program to develop a "proof of concept" prototype filter will be achieved by accomplishing the following specific aims: 1. Selection of candidate media for use in filter based upon physico-chemical characteristics. 2. Evaluate the functionality and biocompatibility of the selected filter media for its ability to remove PEN110 from red cell concentrates without affecting the quality of the red cells. 3. Construct "proof of concept" prototype filters meeting defined performance specifications.